1. Field of the Invention
The present invention relates to a pedal control apparatus of an electronic keyboard musical instrument, and more particularly to a pedal control apparatus of an electronic keyboard musical instrument, the pedal control apparatus controlling an external force exerted on a pedal in response to a depression manipulation of the pedal of the electronic keyboard musical instrument.
2. Description of the Related Art
It is known that an acoustic piano is designed such that a hammer strikes strings in response to a depression of a key to generate a tone. Tones generated by an acoustic piano vary in resonance and magnitude according to the intensity and speed of the depression of keys. Furthermore, an acoustic piano is equipped with pedals for controlling reverberation of tones. In a case of a grand piano, for example, the pedals include a damper pedal, a sostenuto pedal and a shift pedal. In synchronization with a depression manipulation (=performance manipulation) of the pedals by a player, these pedals pivot about fulcrums provided on the main body of a keyboard musical instrument.
Of these pedals, the damper pedal (hereinafter simply referred to as the pedal), which is a pedal for controlling dampers provided in order to stop vibration of strings of a piano, is most frequently used. The dampers are associated with strings in a one-to-one correspondence. Commonly, the damper is released in response to a depression of a key, while the damper presses down strings to stop resonance of a tone in response to a release of the key. The respective dampers are connected to the pedal through some connecting portions. The connecting portions have small spaces between parts thereof, in other words parts of connecting portions are not close contact with each other. Even if the pedal is slightly depressed, as a result, the depression manipulation of the pedal will not be delivered to the dampers. If the pedal is deeply depressed, however, the dampers are removed from all the strings, so that tones will not be stopped by the dampers even if a player releases his fingers from keys. Therefore, all the tones for which the player has depressed the keys are sustained. In this case, all the strings including the strings provided for keys which are not depressed resonate, so that overtones are clearly resonated. As described above, by manipulating the dampers with the damper pedal, the player can enrich expressions of tones.
Therefore, displacement (pivoting) of the pedal from its initial position causes a reaction force (a force exerted in a direction in which the pedal returns, a load applied to a foot of the player) as shown in FIG. 5A being produced on the pedal. More specifically, while the pedal is slightly depressed so that the depression is not delivered to the dampers, the reaction force grows slowly with increasing amount of displacement of the pedal from the initial position. If the pedal is further depressed, so that the dampers start removing from the strings, the reaction force produced on the pedal grows sharply with increasing amount of displacement of the pedal. If the pedal is further depressed, so that the dampers are fully removed from the strings, the reaction force grows slowly again with increasing amount of displacement of the pedal. If the dampers then come into contact with a stopper, the reaction force increases sharply again. In other kinds of acoustic pianos, as shown in FIG. 5B, there is a case in which the increasing rate of the reaction force produced on the pedal according to increasing amount of displacement of the pedal from the initial position is nearly equal to the increasing rate of the reaction force produced on the pedal according to increasing amount of displacement of the pedal from the position at which the dampers start removing form the strings. As shown in FIGS. 5A and 5B, hysteresis occurs in characteristics of the reaction force produced on the pedal relative to the amount of displacement of the pedal, so that the path of the reaction force varies between release of the pedal and depression of the pedal.
As described above, a range AH within which the reaction force grows sharply with increasing amount of displacement of the pedal is the so-called “half pedal range”. The half pedal range AH is a range within which the dampers slightly hold the strings. In the half pedal range AH, the rate of change of the reaction force produced on the pedal is large, compared with an initial pedal depression range A1 (hereinafter referred to as initial range A1) within which the pedal is slightly depressed, so that the depression will not be delivered to the dampers and a latter pedal depression range A2 (hereinafter referred to as latter range A2) within which the dampers are fully removed from the strings to come into contact with the stopper. As described above, there is also a case in which the rate of change of the reaction force in the half pedal range AH is nearly equal to the rate of change of the reaction force in the initial range A1 (except a small range just after depression of the pedal and just before stopping of the pedal) and is larger than the rate of change of the reaction force in the latter range A2. Therefore, the half pedal range AH is a very important range in terms of musical change in any cases. More specifically, it is known that skilled players can perceive the above-described sharp grow of the reaction force to recognize the half pedal range AH, so that they can control the amount of displacement of the pedal in stages within the half pedal range AH to vary the degree of the contact of the dampers with the strings to control timbre and resonance.
There exist electronic pianos which are electronic musical instrument which artificially reproduce timbre, operability and appearance of an acoustic piano. The electronic pianos are designed to make an electronic tone generating portion generate tones in accordance with player's manipulation of a keyboard. Therefore, the electronic pianos do not have any strings. Consequently, the electronic pianos are relatively less expensive than acoustic pianos, rapidly becoming widespread in recent years. As described above, because the electronic pianos do not have strings, the electronic pianos have a pedal structure which is different from that of acoustic pianos. Disclosed pedal structures of the conventional electronic pianos include a pedal unit for electronic keyboard instrument disclosed in Japanese Unexamined Patent Publication No. 2001-22355 and a pedal device of electronic keyboard instrument disclosed in Japanese Unexamined Patent Publication No. 2004-334008.
In the above-mentioned pedal unit for electronic keyboard instrument disclosed in Japanese Unexamined Patent Publication No. 2001-22355, a pedal is urged by a spring so that a reaction force (recovery force) acts when the pedal is depressed. The pedal device of electronic keyboard instrument disclosed in Japanese Unexamined Patent Publication No. 2004-334008 is provided with a first urging member, a second urging member, a lever and the like to realize a reaction force whose rate of change can vary in a single stage according to the amount of displacement of a pedal.
As for the pedal unit for electronic keyboard instrument disclosed in Japanese Unexamined Patent Publication No. 2001-22355, however, the rate of change of reaction force is constant with no variation. As for the pedal device of electronic keyboard instrument disclosed in Japanese Unexamined Patent Publication No. 2004-334008, although the rate of change of reaction force can vary stepwise, the variation is simple, so that the variations in reaction force of the disclosed pedal device are different from those of a pedal of an acoustic piano. Thus, an art disclosed in Japanese Examined Patent Publication No. H7-111631 can be applied to a pedal. More specifically, an external force can be applied to the pedal by an actuator so that the variations in reaction force similar to those of acoustic pianos can occur on the pedal.
Electronic musical instruments are provided with tones of different kinds of acoustic pianos (e.g., Yamaha (trademark) and Bosendorfer (trademark)) as tone generation data to reproduce timbres of the acoustic pianos. In conventional examples, however, even though a player is allowed to select his desired timbre from among different timbres, he cannot change characteristics of reaction force. Commonly, characteristics of reaction force of a pedal vary among manufacturers of pianos as in the case of timbres. The variations in characteristics of reaction force result from variations in structure of a pedal apparatus among the manufacturers (variations in components, load of dampers, coefficient of friction and viscous resistance caused by differences in materials and shape, etc.). In view of reproduction of pianos of various manufacturers, therefore, the conventional examples lack reality in that characteristics of reaction force of pedal cannot vary even though players can select their desired timbres.
Furthermore, variations in characteristics of reaction force of pedal among manufacturers also result in variations in the extent of the half pedal range AH and magnitude of load. In this case, the changing rate of the reaction in the half pedal range AH is different from the changing rate of the reaction in the initial range A1 or nearly equal to the changing rate of the reaction in the initial range A1 by the differences of the structures of the pedal. For a player accustomed to a piano of a certain manufacturer, as a result, characteristics of reaction force of pianos of different manufacturers make him feel strange when he manipulates a pedal in the half pedal range AH. Therefore, the conventional examples are disadvantageous in that he will have difficulty in obtaining his desired timbre and resonance in the half pedal range AH or in that he has to get used to the instrument in order to control the pedal.